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See detailContribution à l'étude des mécanismes de prédation d'Harmonia axyridis (Coleoptera: Coccinellidae) responsables de sa plus grande compétitivité au sein de la guilde des aphidiphages
Durieux, Delphine ULg

Master's dissertation (2008)

The fast spread of Harmonia axyridis (Pallas) (Coleoptera : Coccinellidae) on the continents where it was earlier introduced can be explained by its higher competitiveness compared with indigenous species ... [more ▼]

The fast spread of Harmonia axyridis (Pallas) (Coleoptera : Coccinellidae) on the continents where it was earlier introduced can be explained by its higher competitiveness compared with indigenous species. Here, we compared the Asian lady beetle and indigenous aphidophagous insects according to several factors linked to predation. The three additional indigenous aphidophagous species tested were: Adalia bipunctata (Linné) (Coleoptera : Coccinellidae), Chrysoperla carnea (Stephens) (Neuroptera : Chrysopidae) and Episyrphus balteatus (DeGeer) (Diptera : Syrphidae). The Asian lady beetle consumed more preys than the other studied predators. This was observed with the larval stages but also with adults. Moreover, its larval development and its pupal stage were shorter. A smaller consumption of aphids was observed while the indigenous predators and H. axyridis were brought together. This could be due to a stress induced by one species on the other or to a mutual stress. Finally, an experience using a volatile collection setup revealed that the amounts of released aphid alarm pheromone were smaller when aphids were attacked by H. axyridis than by the indigenous species. The Asian lady beetle reduced the alarm signal emitted by aphids and could like that benefit from more preys. These results contribute to improve the understanding of this invasive species success. [less ▲]

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See detailContribution à l'étude des mécanismes transcriptionnels du facteur de transcription SIP1/ZEB2
Koopmansch, Benjamin ULg

Doctoral thesis (2013)

Lors de la conversion métastatique des tumeurs épithéliales, certaines cellules tumorales acquièrent la capacité d’envahir le tissu sous-jacent et de former des métastases à distance. De nombreuses ... [more ▼]

Lors de la conversion métastatique des tumeurs épithéliales, certaines cellules tumorales acquièrent la capacité d’envahir le tissu sous-jacent et de former des métastases à distance. De nombreuses données de la littérature montrent que l’acquisition de ces propriétés est accompagnée d’un phénomène de transdifférenciation appelé « transition épithéliomésenchymateuse » (TEM), impliquant la perte de caractéristiques de cellules épithéliales au profit de caractéristiques de cellules mésenchymateuses. Parmi les modifications moléculaires caractéristiques de la TEM, on observe une diminution de l’expression de cadhérine E ainsi et l’expression de novo de filaments de vimentine. L’expression accrue de différents facteurs de transcription inducteurs de la TEM est aussi rapportée. SIP1 est un des facteurs de transcription impliqués dans les phénomènes de TEM tumorale. Il a été clairement montré que SIP1 réprime l’expression de la cadhérine E en liant son promoteur. Le mécanisme de répression n’est pas précisément connu, mais il n’implique pas le co-répresseur CtBP. Un modèle de répression suggère que SIP1 empêche l’accès de facteurs activateurs aux promoteurs des gènes réprimés. Les données obtenues au cours de ce travail nous permettent d’appuyer cette hypothèse et impliquent KLF4, un facteur de transcription activateur liant le promoteur de la cadhérine E, dans ce modèle. Nos résultats révèlent en effet une compétition entre SIP1 et KLF4 pour la liaison sur le promoteur de la cadhérine E. Nous montrons aussi que les deux facteurs ont des effets opposés sur l’activité du promoteur de la cadhérine E et que KLF4 n’active celui-ci que lorsque SIP1 ne peut s’y lier. Enfin, nos données nous ont permis de localiser plus précisément la région du promoteur de la cadhérine E liée par KLF4. Cette région chevauche un des sites liés par SIP1. SIP1 est considéré comme répresseur de la transcription, mais les données s’accumulent montrant l’induction rapide de gènes cibles de la TEM, dont la vimentine, suite à une surexpression de SIP1. Nous avons entrepris de mieux comprendre l’activation de la transcription par SIP1 en utilisant le promoteur de la vimentine comme modèle, et par une approche globale à l’aide de la technique de ChIPSeq. Cette partie n’a malheureusement pas atteint ses objectifs. [less ▲]

Detailed reference viewed: 51 (23 ULg)
See detailcontribution à l'étude des paramètres pouvant influencer l'étanchéité des obturations adhésives en dentisterie conservatrice : évaluation des stress thermiques
Gueders, Audrey ULg

Doctoral thesis (2010)

La dentisterie a fortement évolué ces dernières années, notamment dans le domaine de la dentisterie adhésive. Les restaurations directes en composite, collées aux tissus dentaires, sont plus esthétiques ... [more ▼]

La dentisterie a fortement évolué ces dernières années, notamment dans le domaine de la dentisterie adhésive. Les restaurations directes en composite, collées aux tissus dentaires, sont plus esthétiques que les restaurations amalgames et sont devenues tout aussi fiables. La technique de thermocyclage est utilisée de manière courante dans les études dentaires in vitro. Cette technique a été utilisée dans le cadre de cette thèse de doctorat afin d'évaluer l'étanchéité de restaurations adhésives en résine composite. Plusieurs systèmes adhésifs ont été testés ainsi que différentes techniques de restaurations. [less ▲]

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See detailContribution à l’étude des peptides obliques impliqués dans des transconformations
Crowet, Jean-Marc ULg

Master's dissertation (2003)

The study of the amyloidogenic proteins is important to understand the transconformational processes. These proteins have a unique common feature : they undergo a conformational change leading to the ... [more ▼]

The study of the amyloidogenic proteins is important to understand the transconformational processes. These proteins have a unique common feature : they undergo a conformational change leading to the formation of highly structured fibrils that are mainly β conformed. These proteins are difficult to study experimentally due to their low solubility and their tendency to aggregate rapidly. Recently, tilted peptides have been detected in such proteins. These peptides are short fragments (11 to 18 residues) that adopt a tilted orientation when they interact with a hydrophilic/hydrophobic interface. This property is due to the presence of an asymmetric hydrophobicity gradient when they are helical. Those peptides are able to destabilize organized molecular systems. Amyloidogenic proteins containing such peptides are the PrP protein, the Aȕ peptide, and the bacterial prions Ure2p and Sup35p. The presence of such fragments in transconformational proteins has led to the hypothesis that tilted peptides could be implied in the conformational change of amyloidogenic proteins. These peptides could play a role through their destabilizing properties and/or their structural lability. The aim of this work was to detect tilted peptides among other amyloidogenic proteins by molecular modelling. One of the detected peptides is tested experimentally to evidence its lipid destabilizing properties. Five tilted peptides from four different proteins have been detected among 27 amyloidogenic proteins. The tilted fragment from the α-synuclein sequence, a protein involved in Parkinson disease, has been synthetized and tested for lipid fusion. The fusogenic assays pointed out its destabilizing properties. These results support the hypothesis that tilted peptides could be involved in transconformational processes. [less ▲]

Detailed reference viewed: 12 (2 ULg)
See detailContribution à l’étude des propriétés anti-inflammatoires de substances naturelles.
Garbacki, Nancy ULg

Master of advanced studies dissertation (2001)

Detailed reference viewed: 7 (2 ULg)
See detailContribution à l'étude des propriétés du mazer
Martin, John ULg

Master's dissertation (2002)

Detailed reference viewed: 18 (4 ULg)
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See detailContribution à l'étude des propriétés insecticides et chimiques d'Eucalyptus saligna du Zaïre
Kambu, Kabangu; Di Phanzu, N.; Coune, Claude et al

in Plantes Médicinales et Phytothérapie (1982), 16(1), 34-38

The oil of Eucalyptus saligna ( collected on the campus of the University at Kinshasa ( Zaire or Democratic Republic of Congo) has insecticidal properties (against flies, lice, mosquitoes, bed-bugs, black ... [more ▼]

The oil of Eucalyptus saligna ( collected on the campus of the University at Kinshasa ( Zaire or Democratic Republic of Congo) has insecticidal properties (against flies, lice, mosquitoes, bed-bugs, black-beetles) and contains mainly : 1,8-cineol, alpha-pinene,borneol, alpha-terpineol and linalol. [less ▲]

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See detailContribution à l'étude des propriétés interfaciales et émulsifiantes des lipopeptides de Bacillus subtilis
Deleu, Magali ULg

Master of advanced studies dissertation (1997)

Detailed reference viewed: 8 (3 ULg)
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See detailContribution à l'étude des propriétés tensioactives et membranaires d'esters dérivés de la glycine bétaïne
Nsimba Zakanda, Francis ULg

Doctoral thesis (2012)

The objective of this doctoral research is to contribute to the study of surface active and membrane properties of esters derived from glycine betaine. In this context, esters of glycine betaine ... [more ▼]

The objective of this doctoral research is to contribute to the study of surface active and membrane properties of esters derived from glycine betaine. In this context, esters of glycine betaine (alkylbétaïnate chlorides: CnBC, n = 10-16) were obtained using a new synthetic methodology. Glycine betaine (activated by thionyl chloride) and the primary fatty alcohols were used as basic raw materials for the chemical synthesis of CnBC. Some parameters to optimize the synthesis were studied, such as the nature of the organic solvent, the temperature, the molar ratio of reactants and the concentration of the latter in the reaction medium. Next, the surface active and membrane properties of CnBC were characterized using several instrumental techniques such as Langmuir film balance, isothermal titration calorimetry, fluorescence spectrometry and zeta potential and particle size measurements. Hexadécylbétaïnate chloride (C16BC) was synthesized with better performance under the following conditions: absence of a catalyst/base, a solvent of medium polarity (2-methyl-2-butanol), a temperature of 45°C, a molar ratio of betainyl chloride/1-hexadecanol of 3/1 and a concentration of reactants of 0.132 mol/L. Decylbetainate chloride (C10BC) dodecylbetainate chloride (C12BC) and tetradecylbetainate chloride (C14BC) were obtained using the optimal conditions for the synthesis of C16BC. Concerning the interfacial organization of CnBC, C10BC and C12BC did not form insoluble monolayers at the air-water at 20°C compared to their counterparts, C14BC and C16BC. The study of the monolayer of C16BC in various conditions of the aqueous subphase showed that the pH and monovalent anions (OHˉ, Brˉ, NO3ˉ, ClO4ˉ) did not influence the behavior of the monolayer compared to that in water with Clˉ as counterion while the temperature beyond 25°C, the divalent anions (HPO42-, SO42-) and the ionic strength of sodium sulfate (Na2SO4) affected it in term of interfacial area occupation of the molecules. Interactions between CnBC and model membranes have shown that in water, CnBC, regardless of the length of the alkyl chain, have highly penetreted into the negatively charged lipid monolayers (dipalmitoylphosphatidylserine and dipalmitoylphosphatidic acid), whereas their penetration was average and low into monolayers formed by lipids with small polar head (dipalmitoylphosphatidylethanolamine and cholesterol, CHOL) and lipid with large polar head (palmitoyloleoylphosphatidylcholine, POPC), respectively. In salted buffer, the adsorption of C16BC at the air-water interface and onto the surfaces of the lipid monolayers was instantaneous, and in all cases, the penetrating power was above the presumed pressure of biological membranes. C16BC formed miscible and stable mixtures with POPC and sphingomyelin while an almost ideal behavior was observed for its mixtures with CHOL. An affinity of C16BC for the membrane bilayer containing CHOL was also observed. The adsorption of CnBC onto the surfaces of bilayers was alkyl chain-dependent. C10BC, C14BC and C16BC did not significantly perturbed membranes even at high surfactant concnetrations compared to C12BC that has highly perturbed membranes without solubilizing them. In all cases, particles of positive charge and larger than those of membrane bilayers prepared were formed in the presence of high amounts of CnBC. [less ▲]

Detailed reference viewed: 72 (6 ULg)